Inhibition of salt precipitation in aqueous systems

Claim 1

Method for dispersing inorganic matter and for inhibiting precipitation of scale, including calcium sulfate scale, in an aqueous system containing calcium sulfate comprising the step of adding to said aqueous system about 0.05 to 500 ppm of a first active material selected from at least one phosphonocarboxylic acid and a second active material selected from at least one polymeric phosphinocarboxylic acid or a salt or a derivative thereof; said phosphonocarboxylic acid is selected from the group defined by the following two formulas: ##STR12## where R is selected from hydrogen; alkyl, alkenyl, and alkinyl radicals having 1 to 4 carbon atoms; aryl, cycloalkyl, and aralkyl radicals; and radicals selected from the following: ##STR13## where R' is selected from hydrogen, alkyl radicals of 1 to 4 carbon atoms, and carboxyl radicals, and where X is selected from the following ##STR14## where the --PO 3 H 2 moiety is the phosphono group ##STR15## wherein said polymeric phosphinocarboxylic acid is defined as follows: ##STR16## where R is selected from hydrogen, straight or branched alkyl groups of 1 to 18 carbon atoms, cycloalkyl groups of 5 to 12 carbon atoms, --OX groups where X is selected from hydrogen, and straight or branched alkyl groups of 1 to 4 carbon atoms, and groups defined as follows: ##STR17## where R 2 is selected from hydrogen, methyl and ethyl groups, and where the sum of m and n is up to about 100; where R 1 is selected from --OX groups where X is selected from hydrogen, and straight and branched alkyl groups of 1 to 4 carbon atoms; and wherein the relative ratio of the active materials is in the range of about 0.1 to 5 weight parts of said polymeric phosphinocarboxylic acid per 1 weight part of said phosphonocarboxylic acid.